1. Field of the Invention
The present invention relates to systems for powering motors for chain hoists that are mounted upon overhead supports and which lift and lower loads.
2. Description of the Prior Art
Chain hoists are utilized in many different applications to raise and lower loads suspended from overhead supports. A chain hoist is comprised of a heavy duty motor housed within a rugged casing and having at least one chain access opening in the casing. A chain may be suspended from an overhead support or from the chain hoist itself to carry a load. In either case the chain is routed around a chain drive internally located within the chain hoist casing. The chain drive gear within the casing is driven by the chain hoist motor.
Chain hoists are utilized extensively and in widely differing applications. They are used in shops, factories, warehouses, shipyards, exhibition halls, and theatrical stage sets. They are also used in numerous other types of commercial and industrial establishments.
The loads that usually must be lifted with chain hoists require rather heavy duty motors. Since the direction of chain movement must often be reversed, the motors that are utilized are typically reversible in direction. In many commercial and industrial applications chain hoists are rated to lift one-quarter of a ton, one-half of a ton and one-ton loads. The most widely utilized, commercially available motors having this degree of lifting capacity are three-phase, 208 V alternating current motors.
To operate such motors a three-phase, 208 volt alternating current power supply is required. While some commercial and industrial buildings are wired to provide such power and have suitable wall outlets to provide three-phase, 208 volt alternating current power, many buildings, and even more often specific rooms within buildings, simply lack wall outlets of this type. Therefore, the use of a conventional chain hoist within many buildings and within rooms within buildings is simply not possible since there is no suitable power supply for the chain hoist motor.
While chain hoist motors can be operated utilizing portable generators, this solution is not at all adequate. Portable generators are expensive, noisy, and create noxious fumes. Moreover, they must be located out of doors in order to vent the exhaust gases created. This often results in long, difficult cable runs.
The present invention provides a very convenient, relatively inexpensive means for providing the requisite power to chain hoist motors. The present invention is a portable alternating current power supply for chain hoist motors that can be operated from conventional single-phase, 110-120 volt, 20 amp alternating current wall outlets. Such outlets are to be found in virtually every commercial and industrial building in this country. The portable power supply of the invention converts this conventional building wall socket single-phase alternating current to a three-phase, 208 volt alternating current output. As a consequence, chain hoist drives can be temporarily brought into a building or room and operated to perform specific tasks despite the absence of any suitable permanent power supply to drive the chain hoist motors. Rather, the portable power supply of the present invention is merely brought into the room, plugged into any 20 amp wall socket outlet, and then is coupled to drive the chain hoist motor. When the task is finished, both the chain hoist and the portable power supply can be quickly and easily removed.
In one broad aspect the present invention may be considered to be a portable three-phase alternating current power supply for a chain hoist motor. The portable power supply is comprised of a portable case for holding electrical components. The portable case includes a control panel that has at least one single-phase power inlet socket, at least one three-phase motor power output socket, and at least one motor control output socket. At least one three-phase inverter is located in the case and is coupled to receive a single-phase electrical power input through the single-phase power input socket. The three-phase inverter provides a three-phase electrical power output through the three-phase motor output socket. At least one motor direction control switch is located in the control panel and is coupled to the motor control output socket. The motor direction control switch has a multiple position selector to alternatively provide up and down signals to the chain hoist motor.
Preferably the power supply of the invention is further comprised of at least one double pole, double throw phase selector switch located in the control panel and connected between the three-phase inverter and the three-phase motor power output socket. The phase selector switch synchronizes chain hoist movement with the labeled direction of the motor direction control selector which is located in the control panel. It also coordinates and synchronizes this movement so as to coincide with associated UP and DOWN indicator lights on the control panel.
Preferably also the portable power supply includes an actuating GO switch in the control panel that is coupled to actuate the three-phase inverter or inverters. Also, an emergency STOP switch is located in the control panel and is coupled in circuit with the motor direction control switch or switches for interrupting both of the UP and DOWN signals to the chain hoist motor. The portable power supply is also preferably provided with electrically operated UP and DOWN indicator lights electrically connected to the multiposition selector for concurrent actuation with the generation of the UP and DOWN signals, respectively. In addition, a delay circuit is preferably coupled between the power input socket and the three-phase inverter.
In another aspect the invention may also be considered to be a portable, three-phase alternating current power supply for operating at least a pair of chain drives independently of each other. A portable power supply of this type is comprised of a portable case for holding electrical components. The portable case includes a control panel that has at least a first single-phase power input socket, at least a pair of three-phase motor power output sockets, and at least a pair of motor control output sockets. Within the case there are at least a pair of three-phase inverters, both of which are coupled to receive single-phase electrical power inputs through the single-phase power input socket. Each of the three-phase inverters is coupled to provide a three-phase electrical power output through a different one of the three-phase motor power output sockets in the pair of motor power output sockets.
At least one pair of motor direction control switches is located in the control panel. Each of the motor direction control switches is coupled to a different one of the motor control output sockets. Each of the motor direction control switches has a multiple positions selector to alternatively provide up and down signals to different ones of the chain hoist motors.
A dual-chain hoist motor power supply is distinctly advantageous when a pair of chain hoists are to be operated in the same vicinity. This quite often occurs in many applications when it is necessary to lift different loads or different ends of the same load in a coordinated fashion. The dual-chain hoist motor power supply not only provides the requisite three-phase, 208 volt alternating current power to both of the chain hoist drive motors, but also permits control of both chain hoist drives independently of each other from the same location. As a result, the manipulation of loads suspended from two separate chain hoists can be easily controlled by a single individual utilizing the control panel of the power supply as an operating control panel.
In a portable power supply for dual-chain hoists of this type, at least a pair of double pole, double throw phase selector switches are located in the control panel. Each different phase selector switch is connected between a single, separate three-phase inverter and a single, separate motor control output socket. An actuating GO switch in the control panel is coupled to actuate all of the three-phase inverters. An emergency STOP switch is located in the control panel and is coupled in circuit with all of the motor direction control switches to interrupt all UP and DOWN signals.
A dual-chain hoist portable power supply of this type may be utilized to provide adequate operating power for two separate quarter-ton chain hoists, two separate half-ton chain hoists, or a single one-ton chain hoist from a single NEMA (National Electrical Manufacturers Association) 110 volt 20 amp alternating current circuit. However, with some modifications, the power supply can be improved even further to provide adequate operating power for two fully loaded one-ton chain hoists.
To achieve this additional operating capability at least a second single-phase power input socket is provided in the control panel. Also, an automatic power selection circuit is coupled between the first and second single-phase power input sockets. The automatic power selection circuit is actuated by a power input to the second single-phase power input socket to automatically divide loads on the three-phase motor power output sockets between the first and second single-phase power input sockets. In the absence of a power input on the second single-phase power input socket, the automatic power selection circuit couples all of the loads on the three-phase power output sockets to the first single-phase power input socket. Preferably a separate delay circuit is coupled between each of the power input sockets and the three-phase inverters.
In still another aspect the invention may be considered to be the combination of at least one chain hoist drive and a portable three-phase alternating current power supply located remotely from the chain hoist drive or drives. Each chain hoist drive is driven by a three-phase electrical motor and has a power input cable and a control input cable coupled thereto. The portable power supply includes a portable case for holding electrical components and includes a control panel with at least one single-phase power input socket, at least one three-phase motor power output socket, and at least one motor control output socket. At least one three-phase inverter is located in the case and is coupled to receive a single-phase electrical power input through the single-phase power input socket. The three-phase inverter provides a three-phase electrical power output through the three-phase motor output socket. At least one motor direction control switch is coupled to the motor control output socket and has a multiposition selector. This selector is located on the control panel and alternatively provides up and down signals to the chain hoist motor. Each power input cable from each chain hoist drives employed is releasably coupled to a separate motor power output socket. Likewise, each control input cable is releasably coupled to a separate motor control output socket.
The invention may be described with greater clarity and particularity by reference to the accompanying drawings.